distance measurement using sine wave

Hi everyone
I want to measure distance using radio waves
I have an antenna transmitter and a receiver antenna, the antenna emits a sine wave and its frequency changes. waves transmitted and reflected by an obstacle, then transmitted to the receiver antenna
wave antenna in both forward and reflected waves
so i want to measure the distance from the antenna to the obstacles they must do like?
in this experiment, I measured S parameters by network analyzer zbv 8
please help me
thanks

quocvietltbu said:

Hi everyone
I want to measure distance using radio waves
I have an antenna transmitter and a receiver antenna, the antenna emits a sine wave and its frequency changes. waves transmitted and reflected by an obstacle, then transmitted to the receiver antenna
wave antenna in both forward and reflected waves
so i want to measure the distance from the antenna to the obstacles they must do like?
in this experiment, I measured S parameters by network analyzer zbv 8
please help me
thanks

Click to expand...

I'm guessing this would work, though I am thinking this up as I go along.

1) Place an object a known disance in front of both the transmit and receive antennas. Make sure its in the far-field.
2) Measure the phase difference between the transmit and receive signal on your network analyser and consider that your zero point.
3) Remove that object, and substitute your object of unknown distance. If the received signal now has a 36 degree phase difference from the transmit, then it must have travelled a distance equal to 36/360=0.1 wavelengths. If the frequency is 150 MHz (2 m wavelength), then that's a total distance covered of 0.1*2=0.2 m, so your object is 0.1 m away.

Obviously you would get the same 36 degree phase shift if the total distance covered was 1.1 wavelength, 2.1 wavelength, 3.1 wavelengths etc. So using multiple frequencies, you should be able to resolve that ambiguity.

I believe if you think about this carefully, you should be able to work out how to do it.

You implied the frequency wave changing. If you actually mean it is changing all the time, and not just a number of fixed frequencies, then I'm not sure how you can measure the S-parameters. But another technique, FM CW radar would then be possible.

I'm no expert on this - I can only think of some ways that seem to me logical.

Dave